Channel sounding techniques for a wireless communication system

Abstract

A technique for channel sounding in a wireless communication system includes determining respective geometries of multiple subscriber stations with respect to a serving base station. Respective time periods for sounding a channel between the multiple subscriber stations and the serving base station are then set based on the respective geometries of the multiple subscriber stations.

What is claimed is: 
     
       1. A method of channel sounding in a wireless communication system, comprising: determining respective geometries of multiple subscriber stations with respect to a serving base station; and setting, based on the respective geometries determining, respective time durations periods for sounding a channel between each of the multiple subscriber stations and the serving base station. 
     
     
       2. The method of  claim 1 , wherein the setting further comprises:
 setting, based on the determining, a first time duration for sounding the channel between a first subscriber station, included within the multiple subscriber stations, and the serving base station; and 
 setting, based on the determining, a second time duration for sounding the channel between a second subscriber station, included within the multiple subscriber stations, and the serving base station, wherein the second time duration is greater than the first time duration and the second subscriber station is located at a lower geometry with respect to the serving base station than the first subscriber station. 
 
     
     
       3. The method of  claim 1 , wherein the setting further comprises:
 assigning respective channel sounding burst schedules to the multiple subscriber stations for the channel over respective integration time periods that are less than a coherence time of the channel, wherein a number of subcarriers assigned to the channel is not less than a minimum number for implementing code division multiplexing for the multiple subscriber stations assigned to the channel; and 
 communicating, to the multiple subscriber stations, the respective channel sounding burst schedules. 
 
     
     
       4. The method of  claim 1 , further comprising:
 transmitting, from the multiple subscriber stations, respective channel sounding bursts on the channel based on the respective channel sounding burst schedules. 
 
     
     
       5. The method of  claim 4 , further comprising:
 receiving, at the serving base station, the respective channel sounding bursts from the multiple subscriber stations on the channel; and 
 characterizing, for the multiple subscriber stations, the channel based on the received respective channel sounding bursts, wherein the characterizing includes determining a carrier to interference and noise ratio for each of the multiple subscriber stations. 
 
     
     
       6. The method of  claim 5 , further comprising:
 integrating multiple channel sounding burst symbols, included within the respective channel sounding bursts, over integration time periods that are inversely proportional to the respective geometries of the multiple subscriber stations with respect to the serving base station. 
 
     
     
       7. The method of  claim 4 , wherein at least some of the multiple subscriber stations are assigned to a same portion of an uplink subframe of the channel and the transmitting further comprises:
 transmitting, from each of the multiple subscriber stations that are assigned to the same portion of the uplink subframe, respective orthogonal channel sounding symbols, included within the respective channel sounding bursts, based on the respective channel sounding burst schedules. 
 
     
     
       8. The method of  claim 7 , wherein the respective orthogonal channel sounding symbols are created from a channel sounding reference signal sequence using cyclic shifts. 
     
     
       9. The method of  claim 8 , wherein one or more blank cyclic shifts are employed in creation of the respective orthogonal channel sounding symbols, and wherein the method further comprises:
 determining a carrier to interference and noise ratio associated with each of the multiple subscriber stations based on the one or more blank cyclic shifts and the respective orthogonal channel sounding symbols. 
 
     
     
       10. The method of  claim 1 , wherein the respective time durations correspond to one channel sounding symbol for at least a first one of the multiple subscriber stations and to multiple channel sounding symbols for at least a second one of the multiple subscriber stations. 
     
     
       11. A method of channel sounding in a wireless communication system, comprising: receiving, at multiple subscriber stations that are assigned to a same uplink channel, respective channel sounding burst schedules; and transmitting, from the multiple subscriber stations, respective orthogonal channel sounding symbols on the uplink channel based on the respective channel sounding burst schedules, wherein the respective orthogonal channel sounding symbols are created from a channel sounding reference signal sequence using cyclic shifts and include one or more blank cyclic shifts that are not assigned to one of the multiple subscriber stations; determining respective geometries of the multiple subscriber stations with respect to a serving base station; assigning the respective channel sounding burst schedules to each of the multiple subscriber stations for the uplink channel over respective integration time periods that are less than a coherence time of the uplink channel; and communicating, to the multiple subscriber stations, the respective channel sounding burst schedules. 
     
     
       12. The method of  claim 11 , further comprising: receiving, at the serving base station, the respective orthogonal channel sounding symbols from the multiple subscriber stations on the uplink channel; and characterizing, for the multiple subscriber stations, the uplink channel based on the received respective orthogonal channel sounding symbols, wherein the characterizing includes determining a carrier to interference and noise ratio for each of the multiple subscriber stations. 
     
     
       13. The method of  claim 12 , further comprising:
 integrating the respective orthogonal channel sounding symbols over the respective integration time periods, wherein the respective integration time periods are inversely proportional to the respective geometries of the multiple subscriber stations with respect to the serving base station. 
 
     
     
       14. The method of  claim 13 , wherein the respective integration time periods correspond to one channel sounding symbol for at least a first one of the multiple subscriber stations and to multiple channel sounding symbols for at least a second one of the multiple subscriber stations. 
     
     
       15. A wireless communication system, comprising:
 a base station configured to determine respective geometries of multiple subscriber stations with respect to the base station; and 
 a scheduler configured to set respective time durations for sounding a channel between the multiple subscriber stations and the base station based on the respective geometries of the multiple subscriber stations. 
 
     
     
       16. The wireless communication system of  claim 15 , wherein the scheduler is further configured to set a first time duration for sounding the channel between a first subscriber station, included within the multiple subscriber stations, and the base station based on a first geometry between the first subscriber station and the base station and set a second time duration for sounding the channel between a second subscriber station, included within the multiple subscriber stations, and the base station based on a second geometry between the second subscriber station and the base station, wherein the second time duration is greater than the first time duration and the second subscriber station is located at a lower geometry with respect to the base station than the first subscriber station. 
     
     
       17. The wireless communication system of  claim 15 , wherein the base station is further configured to communicate, to the multiple subscriber stations, respective channel sounding burst schedules that include respective orthogonal channel sounding symbols for each of the multiple subscriber stations that are to be transmitted on a same portion of the channel. 
     
     
       18. The wireless communication system of  claim 17 , wherein the base station is further configured to receive the respective orthogonal channel sounding symbols from the multiple subscriber stations on the channel and characterize, for the multiple subscriber stations, the channel based on the received respective orthogonal channel sounding symbols, and wherein the characterizing includes determining a carrier to interference and noise ratio for each of the multiple subscriber stations. 
     
     
       19. The wireless communication system of  claim 17 , wherein the respective orthogonal channel sounding symbols are created from a channel sounding reference signal sequence using cyclic shifts and one or more blank cyclic shifts are employed, the base station determining a carrier to interference and noise ratio associated with each of the multiple subscriber stations based on the one or more blank cyclic shifts and the respective orthogonal channel sounding symbols.